There is fear that COVID-19 vaccination could mess up a woman’s menstrual cycle, but a new study is clearing that up with its “reassuring” findings on how the biological preparations tend to affect periods.
Researchers reported Wednesday that they found only a small and temporary change in the menstrual cycle of women who got jabbed against SARS-CoV-2. The team conducted their research with the help of a birth control app called Natural Cycles and monitored nearly 4,000 U.S. women aged 18 to 45 in the course of the study.
The team led by Dr. Alison Edelman of Oregon Health & Science University specifically tracked six menstrual cycles of the women and analyzed how vaccinations impacted their periods, the Los Angeles Times reported.
According to the team, the next period after receiving a COVID-19 shot started a day later than usual, on average. They also observed that there was no change in the number of days the women had menstrual bleeding.
“Based on prospective population-level data, coronavirus disease 2019 (COVID-19) vaccination is associated with a less than 1-day change in menstrual cycle length but no change in menses length,” the team wrote in their brief.
“This is incredibly reassuring,” Edelman told the Associated Press. She noted that their study included women with the “most normal of normal” cycles — averaging around 24 to 38 days — and they compared their data to those of unvaccinated women.
The scientists admitted that some women reported irregular periods or other changes to their menstrual cycles after getting the shots. A subset of 358 women who got jabbed in the same menstrual cycle recorded a delay of around two days on average. About 10% of them had 10 days or more, but their periods returned to normal ranges the following cycle.
The study presents “important new evidence underscoring that any impact of the COVID vaccines on menstruation is both minimal and temporary,” said Dr. Christopher Zahn, of the American College of Obstetricians and Gynecologists, who was not part of the study.
Further research is needed to validate the findings. For Edelman’s part, she is determined to conduct another study focusing on the possible changes in the heaviness of menstrual bleeding in response to the vaccines, or if women who have irregular periods would yield different results.
The study is published in the journal Obstetrics & Gynecology.